Refrigeration



u 20. 1940. H. c. SH'AGALQFF 2,212,211

REFRIGERATION Filed Dec. 8, 1936 ATTORNEY.

Patented Aug. 20, 1940 UNITED STATES REFRIGERATION Harry 0. Shagaloif, Evansville, Ind., assignor to Servel, Inc., New York, N. Y., a corporaton of Delaware Application December 8, 1936, Serial No. 114,225

-'4 Claims.

My invention relates to refrigeration and it is an object of the invention to provide an improvement in thermostatic control of refrigeration apparatus having a plural temperature evapora- 5 tor or cooling element as will appear from the following description and accompanying drawing in which the figure shows a refrigeration system embodying the invention.

The refrigeration system shown in the drawing is generally like that described in U. S. Patent No. 1,609,334 to von Platen and Munters. It is made up of a number of steel vessels and pipes welded together to form an hermetically sealed system. All the spaces of the systemare in open and unrestricted communication so that all parts are at the same total pressure. The system contains hydrogen and a water solution of ammonia or other suitable fluids.

The parts of the system include a generator sorber IS. The generator I9 is heated by a gas burner l4 arranged so that the burner flame is projected into a generator heating flue 15. The evaporator 12 is located in a thermally insulated storage compartment IS. The condenser H is provided with heat radiation fins for cooling by air. The absorber i3 is cooled by a vaporizationcondensation circuit comprising a cooling coil ll arranged in thermal exchange relation with the absorber connected to a condenser l8, this circuit containing a suitable volatile heat transfer fluid such as methyl chloride.

Ammonia vapor expelled from solution by heat in the generator l flows through a conduit IS, a rectifier 29, and conduit 2| into the, condenser II where the ammonia vapor is condensed to liquid. The liquid ammonia flows from the lower end of the condenser ll into the upper part of the evaporator l2.

Hydrogen circulates through the evaporator l2 and the absorber l3 by way of a gas heat exchanger 22. In the evaporator, the liquid ammonia evaporates and diifuses into the hydrogen, producing a refrigeration effect. In the absorber 45 I3, ammonia vapor is absorbed out of the rich gas by weakened absorption solution. The absorption solution is circulated through and between the generator l0 and the absorber l3 by way of a liquid heat exchanger 23, and circulation of the solution is caused by the lifting action of vapor formed in chamber 24 of the generator which raises liquid through a riser 25 into the generator standpipe 26 where the liquid level is such that solution overflows therefrom into the absorber.

M, a condenser ll, an evaporator I2 and an ab- P A vent conduit 21 is connected from the outlet end of the condenser H to the absorber l3 and is provided with a hydrogen reserve vessel or pressurevessel28. The gas burner I4 is controlled by a valve 29 operated by a thermostat comprising an expansible diaphragm 39 connected by a capillary tube 3| to a bulb 32 which is placed in contact with the bottom of the evaporator l2.

The evaporator I2 is shown more or less diagrammatically as a pipe coil having a lower portion 33 and an upper portion 34. The lower portion 33 of the evaporator coil is imbedded in an aluminum casting 35 providing a freezing compartment having shelves for receiving ice freezing trays or the like. The surface of the casting is relatively smooth and presents only a limited surface for heat transfer thereto from air in the refrigerator compartment. The upper end of the evaporator coil is provided with fins 36 providing a relatively extensive surface for cooling air in the refrigerator storage compartment.

Liquid anunonia which enters the upper end of the evaporator coil flows downward in the coil and gas circulating between the evaporator and the absorber flows upwardly through the evaporator coil. The gas in the upper part of the evaporator coil contains a greater amount of ammonia vapor than gas in the lower part of the coil. The partial pressure of ammonia vapor in the gas in the evaporator coil is a gradient so that the evaporating temperature of liquid ammonia in the coil is also a gradient, being higher in the upper or air cooling portion of the evaporator.

The therm'ostat operating the burner control valve is operable to maintain the valve closed for an abnormal period to permit melting of frost on the evaporator l2, the abnormal period being terminated upon a predetermined abnormal expansion of the thermostat diaphragm 30. This thermostatic control device is fully described and 40 explained in an application Serial No. 758,195 of Sven W. E. Andersson, filed December 19, 1934, which is now Patent No. 2,123,921, granted July ,19, 1938, and is shown here only for the purpose of explaining one advantage of the present invention.

The expansible diaphragm operates responsive to the temperature of the bulb on the bottom of the evaporator. In defrosting, the bottom of the evaporator I 2 may have reached a temperature of, say, 40 F. before ice has melted from the upper part of the evaporator where the temperature has not yet reached 40 F. In other words, it is desirable that the thermostat operate responsive to the coldest part of the plural temperature evaporator and the coldest part may vary under different conditions of operation. I therefore place a portion of the capillary tube 3| in contact with an upper or intermediate portion of the evaporator [2. In the drawing this contact of the capillary tube is shown at the" top of the aluminum casting. It could also be made on the top or box cooling portion of the evaporator.

he length of capillary tube held in contact with t e evaporator must have sufficient volume to contain the liquid in the thermostat fluid system under operating conditions. With this arrangement, control of the thermostatic operation of the burner valve is shifted to that portion of the capillary tube in contact with the evaporator a when the point of contact is at a lower temperature than-the bulb.

The invention could be similarly carried out by providing a plurality of branches of the thermostat fluid circuit or providing a number of temperature responsive devices arranged so that control would be responsive only to evaporator temperature at the point of lowest temperature.

What is claimed is: 1. Refrigeration apparatus including a generator, a condenser, an absorber, an evaporator, a

"heater for the generator, a device for controllin the heater, and an expansible fluid thermostat for operating said control device and arranged in contact with said evaporator at a plurality of places, the part of said thermostat at each of said places of contact having sumcient volume to contain all the liquid expansible fluid under operating conditions.

2. An absorption refrigeration system including an evaporator constructed and arranged for flow of inert gas therethrough and downward flow of liquid in the presence of the gas, members including a generator and condenser for supplying liquid refrigerant to the upper part of said evaporator, a heater for said generator, a device for controlling said heater, and an expansible fluid thermostat for operating said control device and arranged in contact with said evaporator at a plurality of points at diflerent elevations, the part of said thermostat at each of said points of contact having suflicient volume to contain all the liquid expansible fluid under operating conditions.

3. Refrigeration apparatus including a cooling element, a device for controlling operation of said apparatus, and thermostatic means for operating said device arranged so as to be subjected to different temperature conditions which may be variously higher and lower than each other at a plurality of places affected by said cooling element, and constructed to respond only to change in the lowest of said temperature conditions.

4. Apparatus as set forth in claimB in which 25 said thermostatic means is'an expansible fluid thermostat in thermal contact with said cooling element at each of said'plurality of places, the part of said thermostat at each of said places having suflicient volume to contain all the liquid expansible fluid under operating conditions.

HARRY c. SHAGALOFFI. 

